The invention relates to a method of producing a daylight projection screen comprised of a lens matrix and a cooperating lens-aperture matrix located at least approximately in the focal plane of the lens matrix.
More particularly, the invention relates to methods of this type wherein electromagnetic radiation is projected through the lens matrix itself to produce the apertures of the lens-aperture matrix.
Still more particularly, the invention relates to such methods wherein the material which forms the lens-aperture matrix undergoes mechanical and/or chemical and/or optical changes in response to such irradiation.
We have considered the possibility of forming a daylight projection screen using a lens matrix which is coated on its back side with a photographic reversal-film emulsion. The projection screen could be formed by projecting light onto the emulsion, through the lens matrix itself, with all portions of the emulsion layer being illuminated simultaneously, and with the projection being performed in correspondence to the geometry of the projection light which will be used when projecting images using the finished screen. After the emulsion has been exposed in this way, it is developed. The development results in the formation of the fixedly secured and properly positioned lens-aperture matrix necessary for producing the requisite image contrast boost.
However, this production technique has important disadvantages. The development process needed for converting the exposed emulsion into an actual lens-aperture matrix is relatively complicated, and therefore not well suited for cheap, mass-production manufacture. Furthermore, problems are presented when the back surface of the finished projection screen is essentially comprised of a gelatin-silver emulsion. Such a material is very unstable and is easily damaged when handled, for example when the projection screen is being cleaned. On the other hand, if a further layer of transparent material is provided over the gelatin-silver emulsion, to protect it from physical damage, this turns out to detract markedly from the contrast boosting effect desired for a daylight projection screen.